The invention is directed to a control plate for a flat plasma screen employing a carrier plate which on one side thereof carries parallel control electrode paths corresponding to the lines of the screen and on the other side of the plate carries a series of parallel control electrode paths which extend in a direction perpendicular to the series of electrode paths on the first side of the plate and correspond to the columns of the screen, with the carrier plate having control apertures extending therethrough located at the intersections or crossing points of the respective series of control electrode paths on the opposite sides of the plate.
A control plate of this type functions to effect the matrix selection of the individual image or picture points of, in this case, a flat plasma screen. By suitable selection of a line and a column, i.e. selection of the corresponding line column electrode paths, the control aperture at the intersection point of the selected line and column electrodes is unblocked or released, whereby electrons from the plasma of the gas discharge space of the structure lying behind the control plate can be discharged into the acceleration space which lies in front of the control plate, wherein they are accelerated and upon striking the adjacent face of the screen generate a point or spot of light (a scanning spot), with the sequential scanning and production of such light points producing the desired video image on the screen. A description of this type of two-chamber operation can, for example, be found in German OS No. 2,615,721. This German publication also illustrates a construction of a control plate comprising a carrier plate formed of glass, with the control electrode paths being disposed on opposite sides of the plate, and the respective control apertures being produced in the plate by means of chemical etching.
Problems arise in the production of etched plates of this type as a result of the necessity of utilizing a glass plate of sufficient thickness to provide adequate stability. It will be appreciated that as the thickness of the plate is increased, deeper control apertures must be etched into the plate, and as a result the underetchings produced under the mask which is used laterally in plate direction, correspondingly increase, resulting in a reduction in the mechanical stability of the plate, particularly with the prerequisite of a sufficiently large number of control apertures, which again is dependent upon the number of image or picture points required, etc. Further, the aperture cross section present must be sufficient to enable as many electrons as possible to flow from the discharge space through the selected control aperture into the acceleration space. However, the size of the control apertures is limited not only by the requirements for sufficient mechanical stability and for sufficient number of control apertures, but also by the requirement that no electrons should be permitted to pass through unselected control apertures or apertures which are only partially selected, i.e. half selected by the application of control voltage to only an electrode at one side of the plate, and further the requirement of the electric penetration factor of the acceleration anode, which is applied to the front plate, through the control apertures into the discharge space remains as small as possible.